This manuscript presents a method for integrating floating photovoltaics (FPVs) into long-term energy planning, addressing rising electricity demands amidst water stress, land competition, and climate vulnerabilities. This integrated framework is applied to four Eastern Nile Basin countries, where renewable technologies are projected to dominate the power mix. Here, FPVs are evaluated for cost-effectiveness, water savings, and land efficiency. The study advances the OSeMOSYS energy planning framework by spatially explicitly modelling water savings and land values for various energy technologies, incorporating CO2 emissions and land use costs in the optimisation. To this end, new methodologies for land-use accounting and FPV potential for reducing evaporation in hydropower reservoirs were developed. We then evaluate FPV potential across a network of hydropower plants, incorporating electricity trade links between basin countries and simulating under different CMIP six climate change scenarios and tax scenarios. Across all scenarios, results indicate that FPVs can cost-effectively provide up to 3% of the region’s electricity generation by 2065, saving up to 376 million cubic meters of water annually. Scenarios introducing carbon and land-use taxes increase FPV’s share in the power generation mix to 4.5% and enable earlier FPV deployment. While climate impacts minimally affect FPV’s role, the technology slightly reduces CO2 emissions (0.4%) and land use (0.8%) in the baseline scenario without taxes. Compared to baseline scenario, a carbon tax alone reduces emissions by 11%–23% but raises land use by up to 8% due to increased renewable technologiesdeployment. On the other hand, land tax alone would reduce land use by 5%–8% with minimal impact on emissions. However, combining land and carbon taxes affects emissions (cuts up to 22%) and land use (a decrease of 1.6% or an increase of 1.2%). The study concludes that FPVs offer a promising solution for cost-effective and sustainable power expansion in the Eastern Nile Basin.